The present invention relates generally to materials that diffuse flowing fluids into a dispersed pattern. In particular, the invention relates to air diffusers for environmental control systems in commercial and residential buildings. More specifically, the invention relates to a fabric air diffuser or a molded diffuser that can be used in place of conventional diffusers. The invention also relates to a method for diffusing air and a method for attenuating the noise associated with flowing air. The invention contemplates the use of any woven fabric or molded material having the shape and geometry described herein. The present invention has additional applications generally involving controlling the flow of fluids in general from both enclosed and unenclosed spaces.
Air diffusing systems are designed to redirect air that is supplied from a duct in the ceiling of the enclosed environment. In general, it has been known that air diffusers redirect air as it flows into a room from a ceiling mounted supply duct. Without a diffuser, the air provided by the duct will flow straight down into the room. This can cause undesirable air drafts or turbulence within the room, as well as poor thermal mixing, and poor changeover of room air.
The prior art diffusers solve this and other problems by redirecting and diffusing the air as it enters the room. To accomplish this goal, the exit xe2x80x9cfacexe2x80x9d of a typical prior art diffuser has an associated group of angled vanes or louvers to alter the air flow direction. In addition or alternatively, directional devices may be found inside the duct above or behind the outlet portion of the system.
Prior art diffusers that utilize angled vanes or louvers include those set forth in U.S. Pat. No. 3,948,155, issued Apr. 6, 1976 (Warren R. Hedrick), U.S. Pat. No. 4,266,470, issued May 12, 1981 (Schroeder et al.), U.S. Pat. No. 4,366,748, issued Jan. 4, 1983 (Wilson et al.), U.S. Pat. No. 5,054,379, issued Oct. 8, 1991 (Franc Sodec), U.S. Pat. No. 5,192,348, issued Mar. 9, 1993 (Craig S. Ludwig), and U.S. Pat. No. 5,454,756, issued Oct. 3, 1995 (Craig S. Ludwig).
Fabric sheets have been used in diffuser systems to filter dust and other particulate matter from the air passing into the room. U.S. Pat. No. 4,603,618, issued Aug. 5, 1986 (Charles W. Soltis), discloses a clean room ventilation system having a fabric sheet fixed above a perforated ceiling grid. The fabric sheet filters the air and provides a uniform laminar flow of air into the room. The fabric sheet and perforated grid extend across the entire ceiling, and air flows from the ceiling straight down into the room.
The prior art air diffusers have many problems. They often accumulate dust, which tends to build up around the angled vanes. In addition, the prior art air distribution systems tend to be noisy.
Fabrics have also been used to absorb sound. U.S. Pat. No. 4,152,474, issued May 1, 1979 (Cook, deceased et al.), discloses an acoustic absorber which comprises a substrate having a plurality of openings. An organic polymer coating covers the substrate and partially fills the openings in the substrate.
It is an object of this invention to provide a pore-containing sheet or web for changing the flow of a fluid. A fluid flowing into the web at an angle essentially normal to the web surface is redirected as it passes through the web. The fluid exits the web surface in a direction that is lateral to the web surface and radially outward from the center of the web.
Another object of the invention is to provide a diffusion web that significantly reduces the noise commonly associated with the passage of air through a diffusion system, particularly as produced by the angled vane type diffusers.
A further object of this invention is to provide a means for altering the radial distribution of the fluids redirected by the web. By angling the feed duct or blocking a prescribed portion of the web, it is possible to control the radial pattern of thrown fluid to make it non-uniform in directionality while still essentially radial and laterally outward from the diffusing web.
Further objects of the invention include a variety of new end use applications for the pore-containing web diffuser. By varying the material making up the diffuser and choosing a particular geometry for that material, it has been found that the diffuser may be used for many different end uses involving the redirection of fluids passing through the diffuser. The invention also has applications for controlling the flow of fluids where the fluids flow from both enclosed and unenclosed spaces.
The present invention concerns a pore-containing web material that has the ability to diffuse fluids passing therethrough. In one embodiment of the invention, the pore-containing web is composed of a fabric sheet that is employed as an air diffuser. In this embodiment, the diffuser includes a frame adapted to be connected to the end of an fluid (air) supply duct. The fabric sheet changes the direction of air flow upon exiting the sheet. More particularly, the fabric sheet redirects and scatters air flowing into the sheet. Upon exiting the weave openings, the air flows laterally to the sheet and radially outward from the sheet in all directions. The degree of lateral deflection depends on flow rate, weave opening size, and fabric thickness, as well as the properties of the fluid itself, such as density.
The pore-containing web may be constructed from a variety of materials, including for example, glass fibers such as fiberglass (a non-combustible material), nylon, plastics, elastomer, polyester, polyvinyl chloride (PVC), polyethylene, polypropylene, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), acrylic polymers, polystyrene, acrylonitrile/butadiene/stryene rubber (ABS), polyphenyl sulfide (PPS), polyaramid, fibrillated polytetrafluoroethylene (PTFE), metal, ceramics, carbon fibers and woven and nonwoven natural and synthetic fibers and blends thereof.
The pore-containing web optionally may be coated with a material including, for example, halogenated and non-halogenated plastics, silicone, epoxy, polyimide, polyamide, elastomer, nitrilerubber (NHBR), neoprene, ethylene/propylene/dienerubber (EPDM), any thermoplastic elastomer, polyurethanes and aqueous or solvent based polymer coatings.
The web may be coated with a soil resistant material. A soil-resistant material, such as polytetrafluoroethylene (PaTE), inhibits adherent dust and other particulate matter from accumulating on the fabric and, therefore, eases cleaning the diffuser. Other flouropolymers may be used, including a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP), polyvinylindene fluoride (PVDF), copolymers of tetrafluoroethylene and perfluorinated alykyl vinyl ethers (PFA), terpolymers of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV), polychlorotrifluoroethylene (PCTFE), fluoroelastomer (FKM) and perfluoroelastomer (FFKM).
Other surface treatments may be applied to reduce accumulation of particulate matter, inhibit biological growth, and/or prevent degradation. Such surface treatments include surface active agents, biocides (e.g., Dowicide(copyright) made by Dow), fluorinated surfactants, antistatic coatings, water and/or stain repellent coatings (e.g., fluoroacrylates such as Scotchguard(copyright) made by 3M and Zonyl(copyright) made by DuPont), coatings capable of generating heat, heat and/or electrically conductive coatings and dyes.
A further aspect of the invention is that the pore-containing web diffuser can be used for attenuating the noise associated with a fluid (such as air) flowing through a defined volume (such as an air duct). By disposing the pore-containing web (such as an open-weave, fabric sheet) across an entire cross-sectional area of the volume, the web attenuates the noise that is generated by the fluid passing through the diffuser system, as well as any noise generated prior to the diffuser system.
Where the pore-containing web comprises a fabric diffuser for air, the diffuser may be used in place of a conventional, angled-vane diffuser which typically generates a substantial noise as air passes by the vanes. The fabric air diffuser may be employed in a variety of air distribution systems, such as, heating/cooling/ventilation (HVAC) systems.
In the case where the pore-containing web is a fabric sheet for diffusing air, the air flowing from the duct into the woven sheet or web is angularly deflected and flows radially away from the xe2x80x9ccenterxe2x80x9d of the exit face of the web. The externally supplied diffused air and the xe2x80x9cstandingxe2x80x9d room air in front of the exit face collide and mix and flow parallel and radially outward from the web. The invention provides multiple advantages in the realm of air diffusers as well as other potential fluid directing applications. It is the intent of the invention to achieve the lateral direction change and radial pattern for a fluid, particularly air, flowing from a supply reservoir.
In another embodiment of the invention, the pore-containing web of the invention comprises a molded plastic diffusing web. In an air duct application, the molded plastic air diffusing web is installed at the end of an air duct controllably supplying air to an enclosed environment, such as a room or hall.
The plastic molded web of the present invention has an array of numerous openings occupying about 60% of the molded web area, more preferably about 50% of the molded web area or most preferably about 35% of the molded web area. The openings are preferably in-plane with the surface of the molded web. The degree of lateral deflection depends on flow rate, opening size and molded web thickness. The web is formed by compression molding, thus forming a frontal face and a rear face which preferably are used as the entry and the exit surface, respectively.
The molded web may be constructed of a variety of polymeric or non-polymeric materials including plastics, elastomers, fluoroplastics, fluoroelastomers, polyester, PVC, polyethylene, polypropylene, PEEK, PEKK, acrylic polymers, polystyrene, ABS, PPS, and metals or blends thereof In one embodiment, the molding polymer is preferably a thermoplastic and can be treated to be dust repellent and soil and corrosion resistant. A thin coating layer with these attributes can be applied to the molded diffuser web. The coating layer may be composed of halogenated and non-halogenated plastics, silicone, epoxy, polyimide, polyamide, elastomer, NHBR, neoprene, EPDM, any thermoplastic elastomer, polyurethanes and aqueous or solvent based polymer coatings. Particular fluoropolymer coatings include FEP, PFDF, PFA, THV, PCTFE, FKM and FFKM. Certain surface treatments are applied to reduce accumulation of particulate matter, inhibit biological growth, prevent oxidation, and/or prevent degradation. Such surface treatments include surface active agents, biocides (e.g., Dowicide(copyright) made by Dow), fluorinated surfactants, antistatic coatings, water and/or stain repellent coatings (e.g., fluoroacrylates such as Scotchguard(copyright) made by 3M and Zonyl(copyright) made by DuPont), coatings capable of producing heat, heat and/or electrically conductive coatings and dyes.
The molded web may also be used to redirect a fluid flowing into one face and exiting the other face of the web by forcing the fluid to flow laterally and radially outward from the center of the web as the fluid passes through the exit face of the web. For example, air flowing from a duct into the molded sheet or web is angularly deflected and flows radially away from the xe2x80x9ccenterxe2x80x9d of the exit face. The externally supplied diffused air and the xe2x80x9cstandingxe2x80x9d room air in front of the exit face collide and mix and flow parallel and radially outward. It should be noted that for this described phenomenon to occur, the molded sheet must be of a unique aperture configuration, and one not unlike the fabric sheet described above. The face of the molded sheet is planar as a function of molding, and it can be molded in such a way that the geometry of the part helps maintain the flatness of the part, for example, by molding a rib pattern onto the back side of the web. A stiff, yet moldable, web material (for example a metal wire, either as the web, or as part of the web) could also be used to maintain flatness in the web, or could be used for maintaining the web in a non-planar shape if such was desired. The rigid frame can be an integral part of the surface in a compression molded assembly. It is the intent of this invention to achieve the lateral direction change and radial pattern for air flowing from a supply duct into the web exiting from the planar web surface.